Good synthetic diff oil?
 

I'm going to replace my trans and diff fluids soon and I'm a bit confused on what to use for the diff. I have settled on the Ford motorcraft synthetic oil for my tranny, but don't know what to use for the diff. Is it okay to use the Ford oil for the diff as well? Would any synthetic 75w90 oil suffice? Does anybody have any experience with this AMSOIL gear oil?

AMSOIL Manual Transmission & Transaxle Gear Lube 75W-90

Diff is GL5 tranmission is GL4, so it's not a good idea to use the motorcraft fluid in both (also that stuff costs more).

Any 75w90 will work, just make sure it's GL5. Personally, I plan to put in the Redline in the next few days.

I was going to use Redline but there no place around me sells it. I think I might just buy some Mobil 1 75W90 from Autozone.

As 'poacher' said Diff is GL5, Manual Transmission is GL4.

There are plenty of threads on this subject, please search...even look for Sticky DIY's.

Oil grades/types (All Fluids for that matter) for Diffs and Transmissions are identical for all Series RX-8's from 2004 to 2012.

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